Modern times have seen radical changes in traditional values of many cultures. Nowhere have these changes been more profound than in the United States, none more far ranging than those changes related to food preferences, and no particular food more adversely affected than the poultry egg.
To some extent, this remarkable alteration in cultural food preferences is a result of the fabulous selection and variety of new and alternative food products. To a greater extent, perhaps, it has also resulted from underlying pressure on food systems by dense and increasing populations and competition for traditional foods derived from the land and sea.
Above all reasons, the most dynamic has been the healthy life style phenomenon-an icon of eclectic health preferences constituting passionate advocation to spurious recipes for health and longevity based on food selection and exercise. This movement, almost certainly of future historical note, if not derision, may be characterized as both shallow and over simplified. Issues of extreme technical complexity, both positive and negative, entirely beyond the kin of those attempting to respond to them or journalistically pontificating them, have resulted in tidal movements of consumers towards some foods and away from others.
On the other hand, all of this has served as an iambic to distill a number of issues of inescapable importance into focus. Of vast importance to the vitality of our culture, these issues center on an increasing concern about traditional foods as they relate to food safety, raising questions regarding healthfulness versus. safety values of many traditional foods, including adequacy of methods for processing them.
Regulatory agencies have grown in both scope and focus in light of ever increasing public awareness and journalistic inquisition. Expanding to meet their mandates, authorities have brought a new degree of intensity and sophistication to bear in questioning and then setting new bench marks of judgement about traditional food safety values.
Statistics summarizing egg consumption have shown an increasing decline since the famous (or infamous) Framingham study. This decline in consumption is attributed primarily and almost solely to the cholesterol content of a typical egg.
Increasingly, journalistic reports concerning the food safety of eggs have illuminated the issue of transovarian infection of the egg as it is formed. For reasons not entirely clear, diseased hens excrete microorganisms inside the egg. The microorganism in question is Salmonella enteritis (S. enteritis).
Salmonella (S.) are small, gram negative, non-sporing rods that are indistinguishable from Escherichia coli (E. coli) under the microscope or on ordinary nutrient media. All species and strains are currently presumed to be pathogenic for man. As a disease organism, Salmonella produces a variety of illnesses depending on species. S. typhimurium, which translates to Salmonella from Typhus Mary, needs no other explanation. S. typhi causes a classic example of an enteric fever. S. paratyphi type A and type B cause a syndrome which is similar to but milder than typhus. Over 2,000 species of Salmonella are known. The number increases yearly. Reported cases of severe gastroenteritis (stomach flue) have implicated S. bareilly, S. newport and S. pullorum as well. While the mortality range is primarily based on the victim's age and general health category, S. choleraesuis has the highest reported mortality rate at 21%.
S. senftenberg is reputedly the most heat resistant Salmonella known. It is reportedly destroyed at 130.degree. F. (54.4.degree. C.) after 2.5 minutes. It is estimated that S. senftenberg 775W is 30 times more heat resistant than S. typhimurium. Turkeys inoculated with 115,000,000 microorganisms (10 to 11 lb. turkeys) kept at an average internal temperature of 160.degree. F. (71.1.degree. C.) required 4 hours and 55 minutes before the bacteria were destroyed.
The most common food vehicles for food poisoning caused by Salmonella are beef, turkey, eggs, egg products and milk. It is estimated that over 40% of food borne disease outbreaks may be traced to turkey and chicken. Studies of chicken from a typical grocery food counter have shown over one third to test positive for Salmonella S. typhimurium, the most common form found in the U.S.
Over 538 cases of salmonellosis were reported in the U.S. for dairy products--cheddar cheese, raw milk and certified raw milk. Sausages, particularly pork, bacon, frankfurters, bologna and related meat products are subject to similar microbial problems.
Widespread publicity on sickness and deaths from eggs containing S. enteritis in Europe over the past few years has reportedly resulted in a reduction in egg consumption estimated to be as great as 50%.
The problem in Europe and the U.S. is being perceived as chronic, spreading and a major challenge in public health.
Nevertheless, even with the U.S. reduction in consumption attributed to public concerns over cholesterol, approximately 240,000,000 dozen eggs are consumed annually.
Reports by the Center for Disease Control (CDC) have traced development of food poisoning incidents in the U.S. In 1991 there were reported to be 76 cases of regional food poisoning outbreaks resulting in 17 known deaths ascribed to S. enteritis.
The USDA has increased monitoring of poultry flocks. Eleven major flocks have been found to be diseased with Salmonella type E. So far, the incidence of disease seems to be more or less isolated to the northeastern states. However, reports of S. enteritis have been reported as far away as Washington and California. In 1991, there have to date been 104 reports from Washington state and over 400 from California.
A recent article in Nutrition Action Health Letter published by the Center for Science in the Public Interest, July/August 1991 edition, Volume 18, number 6, "NAME YOUR (FOOD) POISON," relates a current trend of growing concern. The article reports that, according to government estimates, 80,000,000 cases of food poisoning yearly result in about 9,000 deaths and several billions of dollars in health costs.
The article claims that the primary causative foods are, in order: dairy products, eggs, poultry, red meat and seafood.
In 1985, 47 people died in southern California from eating raw milk cheese. In 1985, tainted pasteurized milk caused 16,0000 confirmed cases of Salmonella food poisoning in Chicago. Health authorities estimated that 200,000 people may have been affected.
The following quotes from federal USDA inspectors appeared in the article:
"Would you want to go out to a pasture with a chicken, cut him up, then drop him into a fresh manure pile and eat him? That's what the product is like coming from chicken plants today."
"Practically every bird now, no matter how bad, is salvaged."
"I've had bad air sac birds that had yellow pus coming out of their insides, and I was told to save the breast meat off them . . . You might get those breasts at a store in a package of breast fillets."
"I would never, in my wildest dreams, buy cut up parts at a store today."
The article continues " . . . Even the USDA admits that as much as a third of all chicken sold in supermarkets is contaminated. Some surveys put the figure as high as 90 percent . . . "
With respect to consumers who want to continue to use poultry, the article suggests the following:
Always buy the poultry last at the supermarket.
If it will be more than two hours before you are able to refrigerate the chicken, carry an ice chest in your car.
Washing raw poultry may actually help spread bacteria rather than reduce contamination of the surfaces.
Was everything that comes in contact with the poultry with hot water and soap-hands, knife, cutting board, counter, sink--everything.
Remove the skin. Machines at the processing plant which de-feather chickens often pound dirt and feces into the skin pores. Cook the poultry until the juices run clear, i.e., 180.degree. to 185.degree. F. in the thickest part of the meat.
With respect to eggs, the article reports that 1 in 10,000 eggs is contaminated with Salmonella. The average American consumes about 200 eggs per year. Your chances of downing a contaminated egg are 1 in 50.
If you are over 65 or have a disease such as cancer or AIDS associated with a weakened immune system, the article advises: don't eat raw eggs, don't drink egg nog, don't eat Caesar salads, home made mayonnaise or ice cream, or "health" drinks that call for raw egg. Cook eggs thoroughly--solid white and yolk.
With respect to red meat, the article reveals that health food authorities are tracking a "nasty" bacterium, E. coli O157:H7, which has caused food poisoning from raw and under cooked beef, including "precooked" ground beef patties served in restaurants, hotels, schools, and nursing homes. The beef had not been precooked enough to kill the bacteria which is thought to be the leading cause of acute kidney failure in children.
The article continues with respect to fish and shellfish, asserting that these are among the very worst offenders. It ended up suggesting that, if you are over 65 or have a weakened immune system: do not eat raw shellfish, be selective about where you eat fish, and "over" cook any fish or fish products within 24 hours of purchase.
If the foregoing were not bad enough, what future findings will be likely with greater scrutiny of food safety using today's technological capabilities and knowledge base? The current focus is clearly on the obvious microbial troublemakers, but what about others less obvious? What about parasites? Viruses?
If the egg industry cannot answer the immediate challenge and be in a position to deal with future ones, eggs may well disappear from the American diet. This is also true of milk, meat, poultry, fish and many other foods which have as yet not seen the kind of challenge that has been posed to the egg industry over the past few years.
Alarmed by the reports of egg contamination, institutions have began to require liability insurance from egg suppliers. In turn, fierce competition from remaining markets has narrowed profit margins to a point where egg producers cannot profit and comply.
Egg producers point out that it is improper handling itself by the institution which is most responsible for the problem. They cite the eggs all too often seen setting out at room temperature for long periods of time in institutional kitchens, promoting bacterial advancement in even the freshest egg.
The problem is by no means confined to eggs. Increasing incidents of food poisoning and concerns by health officials extend to milk, milk products, cheeses, sausages, fresh meat and many other foods. For example, it is currently being recommended that poultry be cooked "until the meat falls from the bone."
It is also currently believed by many in the food industry, including those in the meat, poultry and egg fields, that ionizing radiation can be utilized to provide safe to eat shell eggs and other foods.
Salmonella is amenable to treatment by ionizing radiation. Doses of no more than 0.5 to 0.75 millirads are sufficient to eliminate salmonella bacteria from most foods and animal feeds. Reported values for treating a variety of products are on the order of 0.5 millirads to destroy 10.sup.7 S. typhimurium in frozen Whole egg, while 0.65 millirad was required to give a 10.sup.5 reduction in bacterial count in frozen horse meat. 0.45 millirad was required to give a 10.sup.3 reduction to bone meal.
However, radiation treatment must be clearly marked on the package according to current FDA statutes, causing a distinct marketing problem. Also, ionizing radiation treatment of shell eggs and other foods at sufficient levels to provide food safety will result in the formation of free radicals, including peroxides. Trapped inside the foodstuff, peroxides alter the natural flavor of the food, causing it to spoil faster due to the formation of free fatty acids and other breakdown products.
Thus, while microbial kill can be facilitated by radiation, the residue peroxides, even in trace amounts, attack lipids and other food components to an extent leading to spoilage from oxidative rancidity. In most cases, the alteration of characteristic sensory aspects resulting from these resides of the food are noticeable immediately after treatment.
Treatment by ionizing radiation is expensive, requiring skilled operators and maintenance staff.
The overall disadvantages mentioned may prove to be sufficient impediments to bar the use of ionizing radiation to provide safe shell eggs for consumer consumption.
While Salmonelias are amenable to irradiation, what about the bewildering host of other common and not so common microbes; Escherichia coliform or complete genera such as Pseudomonas, Streptococcus, Acinetobacter, Proteus, Aeromonas, Alcaligenes, Micrococcus, Serratia, Enterobacter, Flavobacterium and Staphylococcus, to mention a few?
Just as foods all contain some percentage of water of hydration, all foods contain some percentage of dissolved gases. In dry foods such as cereals, the amount of indigenous dissolved gas is small. In wet foods (those containing more that 50% water), however, the percentage of indigenous dissolved gases is significant.
When a liquid such as tap water or the liquid in whole eggs is subjected to a substantial vacuum, it soon begins to boil as the dissolved gases expand and rise to the surface. Heating the product facilitates and speeds up the gas disincorporation process due to concomitant expansion of gas.
The make-up of the gases may be related to the particular food, whether it respires, is viable or not, and whether or not there are symbiotic or indigenous microbial populations associated with the food. The type and concentration of indigenous gas in a food can also be the best indication of the food's condition and safety since the gas complexes change in accord with the chemical processes taking place within the food.
The gases are stored by condensation, Van der Waal's attraction and entrapment within the natural interstices of food. The food type, basic chemistry, pH, condition, percentage of moisture and other factors influence the type and percentage of indigenous gases.
Foods in their natural condition contain different concentrations and types of gas than processed versions of the same foods. Processing sometimes results in substantial additional gas concentrations and can alter significantly the type of gas complex in a food.
The results are sometimes desirable and other times are destructive to overall food safety and keeping quality.
In many instances, a significant portion of the interstitial gases is ambient air. In others, entirely different complexes may be the result of internally generated gas complexes. In food systems which contain any significant degree of oxygen, the potential and type of microbial growth will be influenced as will the ability of basic components of the food to stand up to oxidative processes.
Even small percentages of oxygen (O.sub.2) molecules will, over time, take part in some oxidative breakdown of the food or act as a force in determining aerobic or anaerobic microbial growth. Sometimes referred to as "oxygen tension," this factor is a significant one in defining the characteristics of food safety and keeping quality.
Nowhere is oxygen tension more important than in the lipid portions of foods. The double bonds of lipids are particularly vulnerable to the presence of oxygen, even in minute amounts. The most common result of oxidative rancidity results in the formation of short chain fatty acids. Not only do short chain fatty acids have pronounced and usually unpleasant odors, but many are toxic. Traditional pasteurization, a common food processing technique, addresses only microbial spoilage, sometimes at the expense of promoting premature oxidative spoilage by altering the composition of the gases in the food being processed.
Ozone (O.sub.3) in small concentrations has been employed during cold storage to preserve some foods, such as eggs. The presence of ozone in cold storage air is effective in preventing growth of microbes, including fungus and molds. Foods dipped in ozone impregnated water have been proposed. In these applications, control of microbial spoilage is external to the food product and influences food surfaces, destruction of airborne microbes and microbial spores.
High ozone generating ultraviolet lamps have been used for the same reason by some food industries. Cheese and dairy manufacturing operations frequently employ "germicidal" lamps in packaging and food processing areas to reduce airborne microbes.
Of course, it is the ozone generated by these lamps which assists in controlling airborne microbial contaminates. This, in turn, reduces exposure of the food to potential spoilage organisms.
Ozone is recognized as a sterilant par excellence, particularly for producing potable drinking water. Outside of limited applications for deodorizing food cold storage rooms and retarding some surface growths, it is not, however, been believed applicable to food for preservation.
This belief is based on assertions that ozone has very poor penetrating qualities and is therefore of limited value in treating foods. Also, ozone imparts a characteristic odor to food. And the presence of ozone enhances and accelerates oxidative rancidity.
There are some indications that ozone (O.sub.3) somehow catalyzes or mediates oxygen (O.sub.2) and that it is the oxygen (O.sub.2) which, as matter of fact, demonstrates the primary sterilizing quality.
Nascent oxygen (O) has only a brief half life. While thought to be of importance in sterilization, however, it only plays a role when products are exposed directly to ultraviolet radiation when nascent oxygen is formed on the surface.
A somewhat related technique, employing hydrogen peroxide in conjunction with peroxidases, has proven effective for reducing microbes in milk and liquid egg replacers.
U.S. Pat. No. 4,808,425, Swartzel et. al, summarizes many other references and resources relative to egg pasteurization and adequately points out many of the problems associated therewith.
Liquid whole egg treated with the Swartzel et al. ultrapasteurization process has been produced and distributed, meeting with good commercial success for the reasons anticipated by the inventors. Yet, commercial products produced by the Swartzel et al. process have not adequately resolved many problems attendant with the antecedent products mentioned therein. Off flavors, reduced functionality and general problems related to balancing their ultrapasteurization treatment against organoleptic degradation of eggs has led: to a failure to meet product claims, to customer dissatisfaction and to increased scrutiny of finished products by authorities.
Swartzel et al. do advance the utilization of liquid whole egg products in the right direction. However, as a practical matter, the invention runs into the many limitations attendant with trying to match time and temperature to produce a product which is not decharacterized and is still safe.
Ultrapasteurization as taught by Swartzel et al. is clearly an attempt to ultra-optimize traditional pasteurization, thereby producing egg products which can meet the challenge of a technologically sophisticated and demanding consumer. Swartzel et al. marks a point at which the limits of traditional pasteurization process technology is no longer applicable, a point at which the ultimate limit of the original technology can no longer be utilized effectively.
Swartzel et al. can treat only liquid egg products; this is done by contacting them against a heated surface at high temperatures, i.e., 140.degree. F. (60.degree. C.) for short durations, i.e., less than 10 minutes.
This is not possible with a shell egg. If the outer shell is contacted with a heated surface at the lowest temperature proposed by Swartzel et al., 140.degree. F. (60.degree. C.), the membrane inside the egg would begin to cook while the immediately adjacent albumen would coagulate in layers radiating inwardly. In effect, each layer would act as an insulating barrier for heat transfer; and long before any significant inner portion of the shell egg could reach 140.degree. F. (60.degree. C.), the outer portions would be cooked. Thus the Swartzel et al. process applied to shell egg would simply cook some portion, leaving some portion untreated, or substantially cook all portions.
With liquid whole eggs, the results of applying Swartzel et al. are that the functional and other important aspects of the egg, including organoleptics, baking quality and syneresis after cooking, are radically changed from normal in ways quite obvious to consumers.
Other workers have also stopped short or somehow overlooked important time and temperature conditions which can achieve desired goals in egg technology-maximum safety with minimum changes in the natural product.
For example, the heretofore proposed thermostabilization technique is a method of preserving shell eggs by briefly heating the egg, i.e., 15 minutes at 130.degree.-135.9.degree. F. (54.4.degree.-57.7.degree. C.). It cannot possibly provide a Salmonella free or Salmonella reduced inner egg product. Temperatures at the egg center never achieve 130.degree. F. (54.4.degree. C.), the minimum temperature-needed at 2.5 minutes to kill Salmonella bacteria.
In short, current, state-of-the-art processes for pasteurizing eggs and egg products aim at egg/microbe contact with a critically hot surface for a time sufficient to reduce microbial populations. In the case of whole shell eggs, these prior art processes merely treats the surface layers of a shell egg which is ineffective to destroy microorganisms inside the shell. Also, current USDA guidelines call for the treatment of a whole egg at 140.degree. F. (60.degree. C.) for 3.5 minutes. Such treatment results in irreversible alterations in functionality of shell eggs so processed.
Other workers have approached the problem in the same way. While the temperatures recommended by them vary widely, as do the times, it is clear that none of the time/temperature combinations allow the egg to achieve adequate temperature for enough time to even reduce microbes at or near the center of shell eggs, let alone reach those temperatures there for long enough to substantially destroy microbes of the Salmonella type. It is known, for example, that S. senftenberg requires exposure of at least 130.degree. F. (54.4.degree. C.) for no less than 2.5 minutes. Even the USDA guidelines will not provide a shell egg that would be significantly reduced in Salmonella beyond the immediate inner shell surfaces.
Others have proposed oiling or otherwise surface treating eggs to influence vapor and gas diffusion through the shell. And, at least one method involves cooking or setting the inside albumen into an inner cooked layer as an oiling alternative. None of these processes have met with any significant approval. Nor is it expected that they would.
Improvements to traditional pasteurization techniques have been manifested over the years to obtain important but increasingly modest gains in food safety. However, pasteurization has always been, and still is, limited in that it addresses only one aspect of food safety--control of microbial populations. As discussed above, however, there is another aspect of spoilage just as important--oxidative changes including those resulting in oxidative rancidity. Oxidative damage would be expected to occur in the lipid portion, of a food. However, it has been found that oxidative degradation occurs in carbohydrates, non-lipid volatiles and protein fractions as well.
To a great extent, it is for this reason that atomic or nascent oxygen (O), molecular oxygen (O.sub.2) and ozone (O.sub.3) are universally considered undesirable for use in food preservation with few exceptions.
Some exceptions are where the food value is increased due to accelerated oxidation, such as with some vinegars. This application takes advantage of ozone's known disadvantage when added to food--the production of flavors, odors, textures and tastes associated with accelerated aging or what is usually considered spoilage in fresh foods.
One problem left unanswered by prior art, of course, is that of insuring that not only those microbes on the surface of a shell egg, but those inside, outside and sometimes throughout, including even the most intimate parts of the yolk, are destroyed. While this form of contamination is thought to be far less frequent, it is nevertheless of great concern with respect to food safety. Excreted by the hen at the time the egg is formed, this type of microbial infection is referred to as transovarian infection. Eggs infected in this way are not in the least amenable to control by any known method heretofore proposed. The microbe most commonly known to be involved is S. enteritis.
Little is known about virology inside the egg. Many believe shell eggs to be sterile inside the shell. Needle puncture samples of the inside of an egg including both yolk and white taken under aseptic conditions usually do demonstrate a negative plate count when cultured. Nevertheless, it is well known that, when eggs are broken in quantity, they immediately demonstrate significant gross populations of microbes. It is not unusual to find plate counts ranging from several hundred to many thousands, even when the surface of the egg shells have been cleaned of filth and washed in the best antiseptics known to food science. The occurrence of S. enteritis inside the shell egg, for example, is well documented.
The problem is that egg shells have pores which permit the egg to breathe. Pore holes vary in size, some being larger or damaged. If, when the egg is laid, those holes come into contact with organic refuse in the cage, some microbes contacted are of a size that can fit through those large pores.
Such entry pores only occur randomly on an egg shell surface. Once inside, the microbes are not spread around the interior consistently but are retained in small patches on the inner shell membrane which has yet smaller pores than the shell.
Washing actually spreads microbes more evenly, increasing contamination through greater surface contact with entry pores. When the eggs are cracked, the membrane may be ripped and torn loose, of course. And, when emptied, the eggs may be peppered with this stored innoculum in addition to airborne bacteria.
In addition, there is, of course, active and ongoing gas and vapor exchange between the yolk and white via the vitelline membrane, between the white and the inside of the shell via the outer and inner shell membranes and also between the shell and the outside environment. These processes can also result in microbial contamination that is not reached by known sterilization techniques.
Numerous methods have been suggested interfering with part of this transpiration by plugging shell pores, usually at the outer shell surface. None of these proposed solutions appear to have been found satisfactory.